1. Field of the Invention
The invention relates to a locking assembly for a polyaxial bone anchoring device for use in spinal or trauma surgery. The polyaxial bone anchoring device includes a bone anchoring element with a shank to be anchored in a bone and a head. The head is pivotably held in a receiving part and can be fixed at an angle relative to the receiving part by applying pressure onto the head via a pressure element. The receiving part has a recess with a substantially U-shaped cross-section for receiving a rod. Further, the locking assembly includes a first locking element that cooperates with the receiving part and is configured to fix the rod in the receiving part, and a second locking element configured to be arranged in the first locking element that is configured to fix the head via the pressure element. The first locking element has an engagement structure for a drive tool, and the second locking element is driven upon rotating the first locking element, so that the head and the rod can be fixed in a sequential manner using a tool with a single drive portion.
2. Description of Related Art
US 2003/0100896 A1 describes a bone anchoring device with a shank and a receiving part connected to it for connecting to a rod. The receiving part has a recess having a U-shaped cross-section for receiving the rod with two open legs and an internal thread on the open legs. A locking assembly is provided comprising a nut member with an external thread that cooperates with the internal thread of the legs and a set screw. The nut member has on one end slits for engagement with a screw tool. The shank has a spherically-shaped head that is pivotably held in the receiving part. A pressure element is provided that exerts pressure onto the head when the nut member is tightened. By tightening the set screw the rod is fixed in the receiving part. Hence, the rod and the head can be locked independently from each other.
U.S. Pat. No. 7,972,364 describes a locking assembly for securing a rod in a rod receiving part of a bone anchoring device that includes a first locking element and a second locking element. With the first locking element and the second locking element the head of the bone anchoring element and the rod can be locked independently using a tool with two drive portions.